In dental offices, central vacuum systems are conventionally used to transport materials away from the dental chairs, for disposal. Materials typically transported include gases, aerosols, liquids, slurries, and solid particulates. The gases flow completely through the system to the vacuum source and are exhausted from the vacuum source. However the liquids, slurries, particulate solids, and the like desirably are removed from the system before the vacuum source. Liquid ring (water ring) vacuum pumps can pass both liquids and slurries to a sewage line while large particle sized solids are trapped by a filter (which is serviced periodically), but for other types of vacuum pumps it is necessary to prevent the liquids, slurries and solid particulates from entering the pump.
In typical dental vacuum systems having non-liquid ring type vacuum pumps, liquid and small particle separation is provided by a separator tank. Typically the flow of fluid from the dental operatories passes into the top of the tank, which has a much larger cross-sectional area than the conduit transporting the fluid slurry, and the liquids and particles fall to the bottom of the tank. Periodically the contents of the tanks are emptied into a sewage line.
In all types of conventional dental vacuum systems, some of the slurry particles travelling from the operatories to the vacuum source settle on the bottom of the pipes or other equipment. Occasionally, large chunks of settled debris break loose and become lodged in filters, separating devices, or drain valves. This causes a very significant problem and may result in the break down of the entire vacuum system. Significantly, the particles being transported in the vacuum system, especially the larger particles, also pose a potential pollution problem since they contain metals including silver amalgam (which is primarily silver and mercury), gold, and other precious and semi-precious metals. Not only are these metals a potential significant pollution source, but they have real value and if salvaged can defray system operating costs.
According to the present invention, a dental vacuum system is provided which has a sludge trap means which allows larger particulates, which includes a great deal of metal, from the vacuum source to be collected so that they need not be filtered out or separated out with liquids in a conventional liquid and slurry separator. The sludge trap according to the invention comprises a simple basically static structure which collects the separated metals and allows them to be periodically removed from the system and sent to a salvage facility so that the metals can be recovered. The sludge trap means according to the invention comprises a simple sanitary tee connected at a downwardly extending in-line outlet to a downwardly extending, closed end trap element, preferably a piece of plastic pipe capped at its opposite end. A valve, such as a slide valve, is provided between the sanitary tee and the pipe, and the pipe is connected to the valve by a coupling means, such as a no-hub (quick release) coupling. The sludge trap according to the invention can be used with any vacuum source, is easy to utilize to capture the salvageable material, and provides a container for the salvageable material that may be directly shipped to a salvage facility, is inexpensive and easy to install, and is "fail safe". Unlike a filter, if the sludge trap according to the invention is not emptied and becomes filled to capacity, it will not clog the vacuum line any more than if it were not present at all.
While the sludge trap according to the invention may be used alone in any conventional vacuum system, in non-liquid ring pump systems it is preferably utilized with a particular liquid separating means according to the invention. The liquid separating means is disposed in the fluid line between the dental operatories and the vacuum source downstream of the sludge trap. The liquid separator according to the invention comprises a plurality of downwardly extending tubes, preferably plastic pipes, each having a larger cross-sectional area than the cross-sectional area of the vacuum conduit. The downwardly extending pipes are connected to the elbow of a sanitary tee so that the liquid and smaller particles will move downwardly into the pipes while the gases continue to flow through the in-line conduit formed by the sanitary tees. A common drain is provided at the bottom of the downwardly extending tubes to allow periodic draining of the liquid and collected slurry materials within the separator. While the liquid separator according to the invention is preferably utilized with the sludge trap of the invention, it can be used without the sludge trap too in place of any conventional tank liquid separator.
The liquid separator according to the invention also have a number of advantageous features. It can be used with any vacuum source, and effectively achieves separation while it saves space compared to tank separators. For example it can be wall mounted and extends away from the wall mounting surface only a matter of a few inches. It can easily be custom made in a wide variety of sizes, and is readily constructed from off the shelf plumbing components. The drain may easily be removed for inspection and cleaning, and the drain valve associated with it is kept closed by vacuum, and has a large opening. Therefore if it clogs it tends to "fail safe", in an open position.
The invention also relates to a sludge trap per se, a method of recovering metals from the fluid slurry in a dental vacuum system, and a method of removing liquids and small particles from a fluid slurry in a dental vacuum system, utilizing the equipment as described above.
With respect to the method of recovering metals from a fluid slurry in a dental vacuum system, the method comprises the steps of: (a) Flowing a fluid slurry under the suction of the vacuum source from the operatories toward the vacuum source in a generally linear first flow path along at least a part of the distance between the operatories and the vacuum source. (b) Effecting a change in the direction of the fluid slurry while flowing in the first flow path to cause large particulates, including metals, in the fluid slurry to move downwardly out of the fluid slurry, while the fluid slurry, including any liquid or smaller particles therein, continues in a second flow path. (c) Collecting the separated out large particulates in a vessel below the first flow path. And (d) periodically capping the vessel, removing it from the dental vacuum system, and effecting recovery of the metals from the separated out particles therein.
The method of removing liquids and small particles from a fluid slurry in a dental vacuum system according to the invention comprises the steps of: (a) Flowing a fluid slurry under the suction of the vacuum source from the operatories toward the vacuum source in a generally linear first flow path along at least a part of the distance between the operatories and the vacuum source. (b) Providing a plurality of downwardly directed second flow paths from the first flow path, each of the second flow paths having a larger cross-sectional area than the first flow path, so that liquids and smaller particles will flow in one of the second flow paths while gases will continue to flow in the first flow path to the vacuum source. And, (c) periodically draining the liquids and smaller particles from all of the second flow paths at the same time.
It is the primary object of the present invention to provide for the effective separation of large particulates, including metals, liquids, and small particles, from a fluid slurry in a dental vacuum system, in an effective yet inexpensive and fail safe manner. This and other objects of the invention will become clear from inspection of the detailed description of the invention and from the appended claims.